COMM-PRO

X.25 37XX NAS
NETWORK ACCESS SUPPORT PACKAGES

37XX X.25 Products

The NAS package allows personal computers, asynchronous TTY terminals, BSC 2780/3780 contention mode terminals, BSC 3270 terminals and native SNA PU type 1 and 2 terminal equipment to access host systems via packet switched networks that utilize X.25 link access procedures. Datapac in Canada, Tymnet and Telenet in the United States are examples of networks that employ the X.25 protocol. From the host's viewpoint, there is no distinction between directly connected terminals and those that communicate via an X.25 network.

NAS supports the following X.25 transport protocols:

• ITI - Interactive Terminal Interface (TTY devices)
   TTY devices access NAS using the Interactive Terminal Interface (ITI) and can be operated PC to Host, or Host to Host. Data can be 7/8 bit ASCII and can operate in transparency (binary) mode.

• DSP - Display System Protocol (BSC 3270 devices)
   Display System Protocol (DSP) support is designed to accommodate the North American DSP packet-level protocol for BSC 3270 devices. Network DSP terminals can access either NCP or EP-based host applications. NAS uses the programmed resource facilities of the ACF/NCP Network Extension Option (NEO) for its boundary function processing in order to provide SNA protocol conversion support.

• BPAD - Binary Synchronous PAD Protocol (BSC 2780/3780 devices)
  Bisynchronous Packet Assembler and Dissembler (BPAD) transport protocol is supported for BSC 2780/3780 terminals in contention mode. Network BPAD terminals can access EP-based host applications such as JES.

• QLLC - Queued Logical Link Control (SNA PU devices)
   Qualified Logical Line Control (QLLC) protocol for native SNA terminal support utilizes IBM's QLLC transport protocol. Network QLLC devices can access NCP-based host applications as native SNA terminal equipment.

• PSH - Packet Switched Header (SNA PU devices)
   Packet Switched Header (PSH), the predecessor to QLLC, protocol for native SNA terminal support utilizes IBM's PSH transport protocol. Network PSH devices can access NCP-based host applications as native SNA terminal equipment.

• XPATH - Transparent Path (ITI, DSP, BPAD, QLLC, PSH)
   A Transparent Path Function (XPATH) permits rerouting of DSP (BSC 3270), BPAD (BSC 2780), PSH, and QLLC calls, as well as ITI calls.

• EPMPX - EP Multiplexing Support (ITI)
   EP Multiplexing Support (EPMPX) is an extension to NAS that allow multiple ITI calls to be mutiplexed over one or more EP subchannels.

NAS X.25 also supports the following features:

• NAS can also be used for single-ended multiplexing applications with X.25-based statistical multiplexers in private network environments. 
• Host-initiated sessions are supported by all device types listed above, i.e., Dial CCW for EP or Connect Out for NCP.
• NAS can support the IBM 3600 family of devices as LU type 0. This provides very efficient file transfer capabilities with low, flow control overhead. 
• Continuously Executing Channel Interface utilizing an enhanced version of IBM's CETI protocol standard. Comm-Pro's CETI supports full duplex ASCII devices connected to the FEP via directly-attached lines, or via an X.25 network. It off loads all Unix TERMIO processing to the FEP from Unix-based systems such as Amdahl's UTS system saving Host CPU cycles. 

Last Update - May 21, 1999